Multiple tube gas heating furnace



March 6, 1951 c. KELLER MULTIPLE TUBE GAS HEATING FURNACE 2 Sheets-Sheet1 Filed Nov; 8, 1948 Inuerflzor Curt Keller March 6, 1951 c. KELLER2,544,600

MULTIPLE TUBE GAS HEATING FURNACE Filed Nov. 8, 1948 2 Sheets-Sheet 2 2[l U U 31 27 32 30 30 29 27 I I 8 i a y R N t Invzntor Curc Keller y f7"Aiiornegs Patented Mar. 6, 1951 Curt Keller, Kusnacht, Switzerland,assignor .to Aktiengesellschaft Fuer Technische Studien,

Zurich, Switzerland, a corporation I land of Switzer- ApplicationNovember 8,.19:48.,-'SerialiNo. 59,01 1

:In'Switzerland November 21, I947 11 Claims. (01. "126-109) Thisinvention relates to a'tu'bular gasheaiterr more especially to .a heaterof this kind for, in-

, corporation in agas turbine plant with an indirec't supply of heat tothe working medium.

One object of the said invention is to provide of construction for atubular heater which is suitable for heating air used as the workingmedium in a thermal power plant of the well known kind in which such.Working medium operates in a tubular gas heater in which the heatingtubes though arranged in as 'com'pacta system as possible, are yeteasily accessible. This last-named .feature is particularly valuablewhen the tubular .gas heater is incorporated in aga turbine plant withan indirect supply of heat to the working medium, as, in such caseqtheheater tubes are subjected to severe stresses, on account of 'the hightemperatures attained; thus it is important to be able, when necessary,to repair thetu'b'es or to change them andto clean any 'foul'ed tubes.

Another "object-of this invention is toprovide a tubular gas heater inwhich flue walls and dei'iiector walls -'(which do not participatedirectly in the heat exchange but only cause pressure losses a closedcircuit.

Fig. 2 .as regards its right hand .half, is a plan view of the heatershown in Fig. 1, while the left hand .half of Fig. '2 is a sectionta'kenin the horizontal planes whose positions are indicated b theIineII-JI inFig. '1.

Fig. 3 is a view similar to Fig. .1 showing another (form ofconstruction for a tubular heater adapted to serve the same purpose asthat menon the heating gas side of the heat exchange system 'arereducedto 'a minimum. ffurther object of the invention is to provide a tubular'gas f'h'eatermeeding comparatively :litt-l'e headroom "for dismantlingand having the smallest diameter.

possible :but in "which the parts :subjected to the highest temperaturesshall besable to m'ove'ireely, while the absolute expansions are slight:and the :relative -positions :of the necessary Connecting points:remain practically unchanged.

.Inrord'er to secureaall :these advantages, 1a tubul'a'r "gas heateraccording to the present invention is provided with a removablecombustion "cham- 'ber, which is .co-axial with the: longitudinal axisof said heater, and is in direct communication,

with 'at least onezsystem of heating tubes likewise "arrangedwcoaxiallywith respect to the said longitudinal axis so that its tube :nests aretraversed externally, from the inside to the outside "of the system andmainly ;-in transverse directions, by.

the heating gases issuing iirom the said combus- -tion chamber. In-suchagas beaten-a distributing chamber .-for the gas to be heated maysurround, within a double-walled structural member, .a collectingchamber for the gas brought to the temperature and the pressure needed,I or .in stance, .attheinlet .tora first .expansionstage- The rdistributing chamber and 'the coljlecting chamber may, likewise, becoaxial with the longitudinal axis of the heater.

itioned in connection with the first example, 'While j f Fig.4 is a planview, half .in section, oi'the heater of Fig. 3., the section beingtaken on 'line IVIV of Fig.3. g

In Figs. 1 and 2, which show an oil-fired tubu- '1ar heater, suitablefor heating air, as aforesaid, the reference I denotes a casing elementwhichis coaxial with the'longitudinal axis of the heater .and isinsulated internally. This casing element embodies and contains aco-axial combustion chamber 3 and also carries 'the'burner 2 which workin the said combustion chamber. Reference 4 denotes a second or lowercasing element, which is likewise insulated internally and arrangedco-axially with .respect 'to the longitudinal axis of theheater. Thecasing element l'is connected detachably .(but in gastight fashion) tothe'cas'in'g element 4 which latter surrounds a itubul'arfheating system5 comprising a number of lengths of tubing arranged as compactly aspossible, with the avoidance, so far as this isjposs'ib'le, of deadspaces and bypasses for the heating gases. This heatingsystem 5, alsoarranged cpaxial'ly with 'respe'ct to the longitudinal axis 'of theheater, is provided immediately beyond the combustion chamber '3 so thatits tube nests are system 5 and given up heatto the tubes, escapefromthe heaterthrough a'branch B of the-casing element 4. .Reference .1denotes a double-walled structural member provided at the lower partofthe heater and, again, co-axial with the'lon- .gitudinal axis of thelatter. This-member "I is 'cletachabl connected at the seating 4 to thecasing element '4. Reference 1 denote a distributing chamber provided'in the member 1 for the air which *isfto be ,Fheated and which flowsbranch 8. This air may, for instance, come from the heat exchanger of athermal power plant, in which air, serving as the working medium, flowsin a closed circuit. The inlet ends of the tubes of the system open intothis distributing chamber 1 which concentrically surround a collectingchamber 9 for the air brought to the required temperature in the saidheating tubes and this heated air flows through apipe It) to a pointofconsumption such, for example, as a turbine in a thermal power plantof the kind above referred to.

It will be observed that, in the heater con structed as above described,those parts of the heating tube system 5 throughwhich flows the 'icoldest part of the air to be heated are located nearest to thelongitudinal axis of the heater.

coldest Waste gases impinge upon them.

The air which is required for combustion and i which is preferablypreheated, enters the casing element I through a branch ll, passingfirst into a chamber i2 which co-axially surrounds the combustionchamber 3'. From the chamber l2,

part of the combustion air then flows directly into the combustionchamber 3 through slots .|3 in a partition wall [4 which surroundsthesaid combustion chamber; the other part of said combustion air flowsalong the external surface of said partition wall and hereupon into theheating chamber I6. Additional air for the support of combustion alsoflows directly into the combustion chamber 3 through a branch [5 rightat the top of the heater. This additional combustion air may bepreheated.

These guide plates l1 and [8 are disposed convergently, in such a Waythat they impart the desired velocity to the fire gases and waste gasesflowing between them through the heating system 5. For instance, thevelocity of these gases may be kept constant. The heater may besupported in any convenient manner, for instance, on stanchions as at I9r If the casing element be detached from the 65 casing element 4 it willbring with it the burners 2 and the partition wall l4 surrounding thecombustion chamber 3 so exposing the tube nests of the system 5, andrendering them easily accessible from inside for such purposes ascleaning, overhauling or replacing. Moreover, when necessary, the wholeof the tube system 5 together with the structural part 1 and the plate18 and Wall 19 can be lifted bodily out of the casing element 4, theheadroom needed for this dismantling operation being substantially lessthan in the case of tubular gas heaters of the longitudinal flow type inwhich the wall surrounding the combustion chamberextends far deeper intothe heating chamber.

Owing to the symmetrical arrangement of the nests of tubing in thesystem 5 and of the chambers I and 9 relatively to the longitudinal axisof the heater, free movement ofthese tube nests and of the structuralpart I "surrounding these 4 said chambers in permitted; thus therelative positions of the connecting flanges on the parts in questionremain unchanged, because all radial expansions proceed outwards fromthe longi- 5 tudinal axis aforesaid.

The tubular heater shown in Figs. 3 and 4 is intended for a hot airturbine plant in which the expanding air is re-heated at least once. Twosystems of tube nests 20 and 2| each as compact it) as possible, artherefore provided, both systems being arrangedco-axially in relation tothe longitudinal axis of the heater. The system 2| surrounds the system20 for the greater part of the length of the latter. The high pressureair to be heated flows through a branch 22 into a distributing chamber23 in a double-walled struc- --tural member 23, which is arrangedco-axially inrelation to the longitudinal axis of the heater, and theinlet ends of the tube nests comprised in the system 2| open into thesaid chamber 23 The air, brought to the required temperature in thesystem 2|; passes into a collecting chamber 24 which is locatedin, theinnermost part of the structural member 23 and is surrounded con- 25centrically by the aforesaid distributing chamber 23 From the collectingchamber 24 the heated air flows through a pipe 25 to a high pressureturbine (not shown) in which it expands to a certain extent, coolingdown as it does so. This expanded air then flows through a branchfl26into a distributing header 2'! belonging to. the

. s econd system 20 of heating tubes. From said header the air passesinto and through the individual tubes of the system 2!] and is thusreheated and delivered into a collecting header 28,

out of which it passes through a branch 29 and a pipe (not shown) to alow pressure turbine (likewise not shown) in which machine it expandsstill further.

The distributor 21 and the collector 28, on

. which the tube nests of the system 20 hang, are

arranged inside an upper casing element 30, being movably connectedthereto, as is indicated by dot and dash lines 3| and 32 in Fig. 3. Theupper casing element30 of the heater is detachably mounted on'a lowercasing element 33 to which also the structural member 23 is detachablysecured. A hood 34, which contains the burners 6o 35 and surrounds acombustion chamber 36 is detachably connected tothe casing element 30.By a suitable inclined arrangement of guide plates 3-8 and 39 (whereofthe guide plate 38 is detachably fixed to the element 33 while the guideplate 39 is connected to the structural part 23), it is possible toimpart to the fire gases and waste 1 gases passing, in the main,transversely through the systems 20 and 2|, a desired velocity at allpoints of the path in question.

In the type of construction last described the two heating tube systems20 and 2| are'also in direct communication with the combustion chamber36. At the same time, the combustion chamber 36 and the systems 20, 2|and the structural 55 member 23 are all arranged in co-axial relation tothe longitudinal axis of the heater. The tube nests of the two systems20 and 2| are, as aforesaid, traversed,'in the main, transversely fromthe inside to the outside bythe fire gases and waste gases, the latterpassing out through a branch 31.

On disconnecting the hood 34 from the casing element 30 the combustionchamber 36, toget her withthe burners 35, canbe lifted out in the'upward direction and the tube nests of the "system ,5 :20 are thenaccessible from the inside "of the heating "ch-amber. Kfter liavin'g'separated the "casing elements 3 6 "and 3 3, the heating "tube system2!! can be lifted out upwards, quit-e independently'of-the system 2'!this renders the tube nestsof the said system 2i freely accessible fromthehealtin'g'c'l'iairnber. Finally, after-breaking the jdintbe'tw'eenthe structural member 23 and the casingelementtt, the second heatingtub'e system 2i and, with it, the "structuralpart "23 may "alsobedrawnout'upward's. The' headr'oom necessary for the removal of these variouspafts is comparatively small.

The -fact that, in both the heaters above described, a comparativelysmall amountcf space z'is' requiredto make the heating tube systems"accessible from the heating chamber, and to en- :a'ble themto beremovedfif necessaryis o'f'par- "ticfilar importanceinthe case oftubular heaters I "installed in ships, in'which'a's a rule'spaceis very's'tfictly limited.

Instead of the oilfurnaces show'n inthe'fi ures, furnaces for otherfuels, such "for example, as Ipulverised coal or gases maybe used.

"Under certain circumstances, waste gases which escape from the heatingchambers of the beater. may be returned to the combustion chamberinorder to help to support combustion. Thus in the case of a heaterconstruction as in Figs. 1 and 2, for example, such waste gases willbein- "troduced'through"thebranch i l, while preheated fresh air can beintroduced through the branch I5. With the h'elp difii'e'turn'ed fluegases or fresh cooling air flowing over the external surfaceof :1 a

L for r'einovailupo'n 'sep'ara'tion'of said parts.

"the partition wall bounding the combustion -chamber,-it is possible toproduce, in the heat ng chamber, which is always indirect communicationwith the combustion chamber, such a temperature that the radiant heatemanating from the said heating chamber shall not be dangerous to thetube nests of the heating system or heating systems.

Since, in a tubular gas heater according to the present invention, thepressure losses on the heating gas side can, as already stated, be keptcomparatively low, a heater of this kind is particularly well suited forcases in which the heating chamber is supercharged, that is to say,where a pressure higher than atmospheric pressure is maintained in thischamber. Under such working conditions it is important to be able tooperate with low pressure losses in the heating chamber, because theoutput of the turbine which drives the supercharging compressor and isitself driven by the waste gases from the heating chamber will begreater the greater the residual pressure of the waste gases.

What is claimed is:

l. A heater intended for heating gases and comprising in combination agenerally cylindrical casing, closed at its ends and dividedtransversely into first and second normally connected but separableparts, the first of said casing parts having a ported, open-ended,tubular projection extending inward from its closed end and dividing acombustion chamber within said tubular projection from an annularcombustionair chamber which encircles the same, and the second of saidcasing parts enclosing a heating chamber into an unobstructed axialportion of which combustion products may flow in an axial direction fromsaid combustion chamber; com bustion burners arranged to operate in saidcombustion chamber; a connection for supplying air 6 to *said annurarchamber; tubular 'he'alt transfer units arranged within-saidheating*charnb'er anrl surrounding said unobstructed axial portion;

two annular --generally conical baffles-so mounted 5 'in saidheatingchamberasto converge-outward and to lap corresponding opposite endportions of said tubular heat tra ns-fer units, the first of said"baiiie'sextending from the peripheralwall of the cylindrical casingnearly to the ppen end of "the "tubular-combustion chamber from which itis spaced "to "afford "an annular entrance passage '"for secondary "air,and the second of "said "baiiles extending nearly but not quite to "the--peripheral wall *of'said casingto define "behind the battle an"dfft'ake space "to which products 'of combustion can flow ast the"periphery of the baiile after 'svieeping'thesurface of said heattransfer units;

means providing an outlet from said o'fitake "spa e"; and connectionsfor leading gas to be heated to and from said tubular heat transferunits.

2. The'com'bination defined in claim l'in which the tubular heattransfer units are in the form "of tubes bent "to form .radi'allyarranged flat "coils having passes which are approximately parallel withthe axis or the heating chamber, and the course of gas to beheatedthrough 'said 00115 is that it first traverses a 'passadjacent saidunobstructed axialportion of "the heating cham- "her and next traversesa pass adjacent "the wall "the CSISl'l'l'g.

The combination d'efined'i'n claimlfinwlii'ch the first pane "isretained in the joint between the *two separable casing-'partsso as tobe freed 4. The combinationdefinedin "claiml in which the tubular heattransfer units, and the second -ba'file-are constructed as a unit withand are supported by a manifold arranged to serve "as "the connectionsforleading the gas to be heated to and from the tubular units, the unitstructure so formed being removably mounted in said cylindrical casing.

5. The combination defined in claim 1 in which the tubular heat transferunits, and the second baffle are constructed as a unit with and aresupported by a manifold arranged to serve as the connections for leadingthe gas to be heated to and from the tubular units, the unit structureso formed being removably mounted in the second of said casing parts andthe first baffie is retained in the joint between the two separablecasing parts so as to be freed for removal upon separation of saidparts.

6. The combination defined in claim 1 in which the connections forleading gas to be heated to and from the tubular heat transfer unitscomprise a double walled unit affording two manifold spaces, oneenveloping the other, to which spaces the tubular heat transfer unitsare connected in parallel.

7. The combination defined in claim 1 in which the connections forleading gas to be heated to and from the tubular heat transfer unitscomprise a double walled unit affording two manifold spaces, oneenveloping the other, to which spaces the tubular heat transfer unitsare connected in parallel, said double walled unit serving as the solesupport for said tubular units and being bodily removable from thecasing therewith,

8. A heater intended for heating gases and comprising in combination agenerally cylindrical casing, closed at its ends and constructed inseparable parts, one end part being formed with a ported open-endedtubular projection ex- -tending inward from its closed end and dividinga combustion chamber within said tubular projection from an annularcombustion-air chamber which encircles the same, and the other end partenclosing a heating chamber into the unobstructed axial portion of whichcombustion products may flow in an axial direction from said combustionchamber; combustion burners arranged to operate in said combustionchamber;

a connection for supplying air to said annular chamber; supply andcollection manifolds adja- I cent said annular chamber; a plurality oflooped heat exchange tube-passes connecting said manifolds andprojecting into said heating chamber in circular series around saidunobstructed axialportion thereof; an annular group of tubular heattransfer units also in said heating chamber I around said circularseries of heat exchange passes; two annulangenerally conical bafiles soI mounted in said heating chamber as to converge outward and to lapcorresponding end portions vof the tubular heat transfer units, thefirst of 'said baffles extending from the peripheral wall I of thecylindrical casing nearly to the open end 'of said combustion chamberand the second of said baffles extending nearly but not quite to 'saidofitake chamber; and connections for leading gas to be heated to andfrom said supply and collection manifolds and to and from said tubularheat transfer units.

9. The combination defined in claim 8 in which the cylindrical casingcomprises two end parts and an intermediate part and the joint betweenan end part and the intermediate part is so 40 located that when theseparts are separated the supply and collection manifolds and the loopedheat exchange tube-passes connecting them may be withdrawn as a unit.

10. The combination defined in claim 8 in which the cylindrical casingcomprises two end parts and an intermediate part and the joints betweensaid parts are so located that separation of the three parts frees forremoval said supply and collection manifolds and the looped heatexchange tube-passes connecting them, and also said first baflie.

11. The combination defined in claim 8 in which the connections forleading gas to be heated to and from the tubular heat transfer unitscomprise a double walled unit affording two manifold spaces, oneenveloping the other,

to which spaces the tubular heat transfer units are connected inparallel, said double walled unit serving to support said tubular unitsand being bodily removable from the casing therewith, said casingcomprising two end parts and an intermediate part and the joints betweensaid parts being so located that separation of the parts frees forremoval said supply and collection manifolds with the looped heatexchange tube passes connecting them and also said first baflle.

CURT KELLER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name 7 Date 2,119,817 Keller June 7, 19382,224,544 Keller Dec. 10, 1940 2,409,801 Ruegg Oct. 22, 1940 2,411,294Ruegg Nov. 19, 1946

